A musician from the United States named Greg Pagel has its own way to prove that the shape of the Earth is round, not flat as said by the adherents of flat earth. He was not careless in doing the proof, because it involves the help of Google Earth and mathematical calculations.
The first thing done by Greg is photographing the scenery in Lake Michigan, United States. He takes pictures of each of the farthest points visible from his standing position, either on the left or right. All photos are uploaded through social media Imgur. Then, there is an image showing the horizon line.
By the way, you see that horizon line? Quite flat right. But, I heard the Earth is round. Have I been lied to? "He wrote in one of his uploads
Then he opened Google Earth to calculate the distance between the two end points he could see from his standing position. He can also know that the distance is 8.4 miles, or about 13.5 kilometers.
Then, he compares the distance with the circumference of the Earth to get the viewing angle he sees through the sequence of photographs. As a result, he came to the conclusion that his point of view was only 0.12 degrees.
Not to stop there, Greg also gives an illustration of how much 0.12 degrees when compared with a full circle representing Earth. If an angle is commonly seen at the intersection between two lines, in this case Greg only displays a thin line because 0.12 degrees is a very small angle.
Therefore, he draws the conclusion that the Earth is seen to have a flat line because humans are only able to see a small part of the Blue Planet, which is actually rounded.